Browse Prior Art Database

Sub-Micron Contact Hole Inspection Monitor Wafer

IP.com Disclosure Number: IPCOM000040959D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fredericks, EC: AUTHOR [+3]

Abstract

This article describes a convenient way for accurately verifying with an optical microscope whether sub-micron contact holes have been opened sufficiently during etch processes. The only method now available for inspecting sub-micron contact holes is with an electron microscope.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 91% of the total text.

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Sub-Micron Contact Hole Inspection Monitor Wafer

This article describes a convenient way for accurately verifying with an optical microscope whether sub-micron contact holes have been opened sufficiently during etch processes. The only method now available for inspecting sub-micron contact holes is with an electron microscope.

The monitor wafer in the preferred embodiment has a layer of metal containing 0.5 to 5.0 percent copper. A layer of insulation, such as silicon dioxide, polyimide, etc. is next applied with a thickness to that of the insulator used in the normal semiconductor process. This in turn is followed by a layer of photoresist which is baked and exposed using the product contact layer mask. Next, the monitor wafer, along with the actual product wafers, is etched to open up the contact holes. Following the etch, the monitor wafer is dipped in a strong acid or base solution and then rinsed and dried.

If the contact holes or vias are open, with no insulator remaining, the acid or base will attack the metal layer and change the color of the metal in the bottom of the via hole, making inspection with an optical microscope possible. Unopened vias will not change colors since the underlying metal layer will not have been attacked. Partially etched vias show a patchy color change, not the uniform color change of totally open vias.

In practice, a metal layer can be any metal which can be attacked and discolored by strong acid or base. The substrate can be si...